1. Field of the Invention
This invention relates to a thermal sensor for detecting temperature distributions, and more particularly to a sensor which is capable of continuously detecting the temperature distribution in a deposit layer on the refractory wall of a furnace with high precision, along with the temperature distribution in the refractory wall itself.
2. Description of the Prior Art
A layer of deposits is apt to be formed on the refractory walls of a blast furnace, particularly, on the refractory wall of a shaft furnace which is cooled through a cooling box. Once formed, such a deposit layer keeps growing in thickness during operation of the furnaces and destabilizes the furnace operation to a considerable degree not only by reducing the capacity of the furnace but also by ununiformalizing the gravitation of the loaded material as well the gas flows in the furnace.
In order to prevent the formation and growth of such deposit layer, it has been the general practice to measure the thickness of the deposit layer by inserting elongated scales through a number of bores in the furnace wall while the blasts are stopped and removing the deposit layer by detonating explosives when it has grown to a certain extent. The use of explosives incurs a large expense for the removing job which only may be in vain in view of the resulting damage to the furnace walls and the danger involved in the job.
However, once the deposit layer has grown to some extent, there has been no method but the above-mentioned method which could remove the deposit layer although it is hazardous to the stable operation of the blast furnace. More particularly, from the stand-point of safe operation, it is desired that the deposits be removed as promptly as possible and in a safe and facilitated manner. For this purpose, the formation of the deposit layer and its condition growth should be kept under observation so that it can be removed by a mechanism before it developes into a substantial thickness, without resorting to explosives.
In view of the difficulty of observing the formation and growth of the deposit layer directly with the naked eye, it may occur to those skilled in the art to provide a sensor projecting from the refractory walls of the furnace, letting the deposit layer grow also on the sensor for judging the condition of the deposit layer on the basis of the information from the sensor. However, no sensors have been developed which have a sufficiently high response and sensitivity in temperature measurement for realizing such a method.